The present invention generally relates to a system for loading a printing plate into a plate imaging device and specifically to a system for automatic loading of plates of various sizes into a plate setter or a printing plate imaging device.
A variety of systems and applications use stacks of sheets or plates, which may be made of metal, paper, plastic and the like. Printing plates (hereinafter singly or collectively referred to as xe2x80x9cplatesxe2x80x9d) are typically stacked in a cassette or similar container which houses the plates and facilitates their protection, transportation and handling.
A specific system using plates generally uses trays having specific dimensions. Trays can usually be set to contain plates of various sizes, but all plates in the same tray are of one size. Usually the plates are manually removed from the cassette or the shipping container and inserted into the trays for use by the system, for example, a plate image system.
Plates are usually packed in the cassette with intermediate paper sheets, hereinafter referred to as xe2x80x98separation paperxe2x80x99. The separation papers are disposed during loading into the imaging device by a mechanism such as described in U.S Pat. No. 6,164,637, assigned to the common assignee of the present invention.
A typical conventional plate feeding system from a tray is shown schematically in FIG. 1. Plates 12 are supplied, within a tray 14, stacked one on top of the other with separation papers 16 between the plates.
Various mechanisms have been developed for removing a single plate 12 from the tray 14 and loading it using loading arm 18 to the loading plane 23 of the imaging system 20. Usually the feeding system includes a mechanism for disposing of the separation paper 16 into a paper bin 22 illustrated, for example.
One such system is described in U.S. Pat. No: 5,785,309 assigned to the common assignee of the present invention. The loading method described has the disadvantage in that, if a different plate size needs to be loaded for a subsequent operation, then the tray in use needs to be replaced by a tray containing the required plate size, or the tray itself needs to be replenished with plates of the required size. Replacing cassettes is a costly procedure and time consuming operation.
U.S. Pat. No. 5,367,360 to Mcllwraith et al. describes a method for loading plates from a single tray. In this case, the cardboard shipping container is used as a tray and the plates are lifted and loaded vertically by a vacuum system.
The use of several trays with the same system is known in the art of copiers, for example, where paper is loaded selectively from different trays. The trays are stacked one on top of the other, each having a separate loading mechanism.
U.S. Pat. Nos. 5,655,452, 5,738,014 5,791,250, 5,788,455 describe an apparatus and method of loading plates from a plurality of trays into an imaging device. The trays are stacked one on top of the other and moved by an elevator mechanism to allow a loading arm to enter between the trays and pick-up a specific plate.
Trays containing printing plates are heavy and bulky, and moving such tray up and down requires complicated and expensive mechanism and is time consuming. There is, thus a widely recognized need for an automatic and efficient handling system of feeding plates of various sizes, without the need to move trays. consuming There is, thus a widely recognized need for an automatic and efficient handling system of feeling plates of various sizes, without the need to move trays.
The present invention discloses a relatively compact system for automatically feeding plates of various sizes from a group of staggered trays.
The present invention provides an automatic plate feeding system, which can be used to automatically feed plates of various sizes into a printing plate imaging device.
According to the present invention, there is provided a plate feeding system for grasping and moving a plate from a stack of plates housed in a plurality of trays. The stack of trays are static and staggered.
The system includes a plurality of trays staggered one on top of the other, wherein at least two of the plurality of trays contain plates of different sizes, the plates usually have separation papers interposed there between; and an arm mechanism for loading plates from the trays and feeding them to an imaging device.
The arm mechanism includes a plate grasping member for grasping the plate and a separation paper disposing system. The grasping mechanism is movable perpendicularly to the arm by a vertical rod which is movable by the carriage. The carriage is movable along the arm which is typically parallel to the plates.
The trays are staggered in a way that the grasping mechanism can be brought to each of the trays"" openings, grasp a plate and feed it to the imagesetter, or grasp a separation sheet and dispose it into the paper bin.
According to further features in the preferred embodiment of the invention described below, the plate grasping member is an array of suction cups.